Identification of a Third Osmoprotectant Transport System, the OsmU System, in Salmonella enterica

Frossard, Stephen M.; Khan, Aftab Aslam Parwaz; Warrick, Eric C.; Gately, Jonathan M.; Hanson, Andrew D.; Oldham, Michael L.; Sanders, D.A.R.; Csonka, László N.

doi:10.1128/jb.00495-12

Cited by 46 publications

(40 citation statements)

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“…CBS domains are known to control the activity of the ATPase subunit by sensing variations in ionic strength in the cell during osmotic shifts (28)(29)(30), and it has been proposed that CBS domains may be predictors of osmoregulatory activity for the ABC transporter (19,29). The lack of a CBS domain is consistent with emerging data showing that YehZYXW ABC transporters are not involved in resistance to hyperosmotic stress (17,(19)(20)(21), though they share significant sequence similarity to known compatible solute importers.…”

Section: Resultssupporting

confidence: 75%

“…The PBP component of the operon (gene locus bab1_0226) is most closely related to Escherichia coli and Salmonella enterica YehZ, which has been described as a component of a putative compatible solute osmoprotectant transport system, YehZYXW (17)(18)(19)(20). The Yeh system is related in primary structure to the glycine betaine OsmU/ ProU uptake systems of S. enterica and E. coli and the OpuB/OpuC choline transporter of Bacillus subtilis (17,(20)(21)(22)(23). However, the function of YehZYXW in vivo remains unclear.…”

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confidence: 99%

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Conserved ABC Transport System Regulated by the General Stress Response Pathways of Alpha- and Gammaproteobacteria

et al. 2017

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Brucella abortus E1 is an EcfG family sigma factor that regulates the transcription of dozens of genes in response to diverse stress conditions and is required for maintenance of chronic infection in a mouse model. A putative ATPbinding cassette transporter operon, bab1_0223-bab1_0226, is among the most highly activated gene sets in the E1 regulon. The proteins encoded by the operon resemble quaternary ammonium-compatible solute importers but are most similar in sequence to the broadly conserved YehZYXW system, which remains largely uncharacterized. Transcription of yehZYXW is activated by the general stress sigma factor S in Enterobacteriaceae, which suggests a functional role for this transport system in bacterial stress response across the classes Alphaproteobacteria and Gammaproteobacteria. We present evidence that B. abortus YehZYXW does not function as an importer of known compatible solutes under physiological conditions and does not contribute to the virulence defect of a E1 -null strain. The sole in vitro phenotype associated with genetic disruption of this putative transport system is reduced growth in the presence of high Li ϩ ion concentrations. A crystal structure of B. abortus YehZ revealed a class II periplasmic binding protein fold with significant structural homology to Archaeoglobus fulgidus ProX, which binds glycine betaine. However, the structure of the YehZ ligand-binding pocket is incompatible with high-affinity binding to glycine betaine. This is consistent with weak measured binding of YehZ to glycine betaine and related compatible solutes. We conclude that YehZYXW is a conserved, stress-regulated transport system that is phylogenetically and functionally distinct from quaternary ammonium-compatible solute importers.IMPORTANCE Brucella abortus E1 regulates transcription in response to stressors encountered in its mammalian host and is necessary for maintenance of chronic infection in a mouse model. The functions of the majority of genes regulated by E1 remain undefined. We present a functional/structural analysis of a conserved putative membrane transport system (YehZYXW) whose expression is strongly activated by E1 . Though annotated as a quaternary ammonium osmolyte uptake system, experimental physiological studies and measured ligand-binding properties of the periplasmic binding protein (PBP), YehZ, are inconsistent with this function. A crystal structure of B. abortus YehZ provides molecular insight into differences between bona fide quaternary ammonium osmolyte importers and YehZ-related proteins, which form a distinct phylogenetic and functional group of PBPs.

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Section: Resultssupporting

confidence: 75%

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confidence: 99%

Conserved ABC Transport System Regulated by the General Stress Response Pathways of Alpha- and Gammaproteobacteria

et al. 2017

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“…The hypervirulence phenotype of the ⌬metQ strain, which is defective in the transport of methionine, may be metabolically connected with the intracellular polyamine imbalance caused by ⌬potD. YehZ shows high sequence homology with OsmX, which is the osmoprotectant-binding protein of the OsmU transport system (45,59). It was recently found that Salmonella strains lacking OsmU stimulate trehalose accumulation and thereby become resistant to intracellular stressors, such as oxidative stress and acidic pH (45).…”

Section: Resultsmentioning

confidence: 99%

Identification and Characterization of Outer Membrane Vesicle-Associated Proteins in Salmonella enterica Serovar Typhimurium

et al. 2014

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dSalmonella enterica serovar Typhimurium is a primary cause of enteric diseases and has acquired a variety of virulence factors during its evolution into a pathogen. Secreted virulence factors interact with commensal flora and host cells and enable Salmonella to survive and thrive in hostile environments. Outer membrane vesicles (OMVs) released from many Gram-negative bacteria function as a mechanism for the secretion of complex mixtures, including virulence factors. We performed a proteomic analysis of OMVs that were isolated under standard laboratory and acidic minimal medium conditions and identified 14 OMVassociated proteins that were observed in the OMV fraction isolated only under the acidic minimal medium conditions, which reproduced the nutrient-deficient intracellular milieu. The inferred roles of these 14 proteins were diverse, including transporter, enzyme, and transcriptional regulator. The absence of these proteins influenced Salmonella survival inside murine macrophages. Eleven of these proteins were predicted to possess secretion signal sequences at their N termini, and three (HupA, GlnH, and PhoN) of the proteins were found to be translocated into the cytoplasm of host cells. The comparative proteomic profiling of OMVs performed in this study revealed different protein compositions in the OMVs isolated under the two different conditions, which indicates that the OMV cargo depends on the growth conditions and provides a deeper insight into how Salmonella utilizes OMVs to adapt to environmental changes.

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“…Bacteria are often equipped with at least two uptake systems for substances with crucial physiological roles; these systems can possess different affinities, capacities, specificities, and regulation mechanisms to satisfy different physiological needs in the changing environment (48). As for aromatic amino acids, more than one uptake system was demonstrated to exist in C. glutamicum (28).…”

Section: Discussionmentioning

confidence: 99%

Characterization and Molecular Mechanism of AroP as an Aromatic Amino Acid and Histidine Transporter in Corynebacterium glutamicum

Shang

Zhang

et al. 2013

Journal of Bacteriology

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bCorynebacterium glutamicum is equipped with abundant membrane transporters to adapt to a changing environment. Many amino acid transporters have been identified in C. glutamicum, but histidine uptake has not been investigated in detail. Here, we identified the aromatic amino acid transporter encoded by aroP as a histidine transporter in C. glutamicum by a combination of the growth and histidine uptake features. Characterization of histidine uptake showed that AroP has a moderate affinity for histidine, with a K m value of 11.40 ؎ 2.03 M, and histidine uptake by AroP is competitively inhibited by the aromatic amino acids. Among the four substrates, AroP exhibits a stronger preference for tryptophan than for tyrosine, phenylalanine, and histidine. Homology structure modeling and molecular docking were performed to predict the substrate binding modes and conformational changes during substrate transport. These results suggested that tryptophan is best accommodated in the binding pocket due to shape compatibility, strong hydrophobic interactions, and the lowest binding energy, which is consistent with the observed substrate preference of AroP. Furthermore, the missense mutations of the putative substrate binding sites verified that Ser24, Ala28, and Gly29 play crucial roles in substrate binding and are highly conserved in the Gram-positive bacteria. Finally, the expression of aroP is not significantly affected by extracellular histidine or aromatic amino acids, indicating that the physiological role of AroP may be correlated with the increased fitness of C. glutamicum to assimilate extracellular amino acid for avoiding the high energy cost of amino acid biosynthesis.

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Identification of a Third Osmoprotectant Transport System, the OsmU System, in Salmonella enterica

Cited by 46 publications

References 50 publications

Conserved ABC Transport System Regulated by the General Stress Response Pathways of Alpha- and Gammaproteobacteria

Conserved ABC Transport System Regulated by the General Stress Response Pathways of Alpha- and Gammaproteobacteria

Identification and Characterization of Outer Membrane Vesicle-Associated Proteins in Salmonella enterica Serovar Typhimurium

Characterization and Molecular Mechanism of AroP as an Aromatic Amino Acid and Histidine Transporter in Corynebacterium glutamicum

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